As reported by Slevins there:
Ever since the upgrading to the 2.0.2 version of the mod, I haven't gotten any weapon drops from enemies. At all. No shotguns from shotgunners, no H.A.R. from the chaingunner replacements, nothing. I've been playing through several stages of multiple mods, vanilla and custom. Pistol only, running through several stages. Avoiding all statically placed weapon pickups- secrets, etc.
Even under these circumstances, without any shotguns or h.a.r./chaingun in my inventory, no monsters have dropped any weapons. From what's being described, I should at least be seeing at least one drop for a weapon type not held. But the game seems to skip directly to dropping ammo instead. This did not happen for 2.0.0- when I did a brief run through of that version, I got a shotgun drop, a H.A.R. drop, and a repeater by stage 5. This also does not happen when I switch to original Doom monsters- they always drop a weapon, 100% of the time.